The perils of flying

During air travel more than a half of all passengers suffer a degree of hypoxemia that might trigger prescription of supplemental oxygen therapy if it occurred in hospitalized patients. That is the finding of a recent study which sought to establish the effect that air travel has on measured oxygen saturation. 

When flying at maximum altitude, cabins of commercial airplanes are pressurized to an equivalent altitude of 5000-8000 ft. Inspired oxygen is consequently reduced. To assess the impact of this reduced oxygen environment researchers used pulse oximetry to measure the peripheral oxygen saturation (SpO₂) of 84 apparently healthy passenger volunteers before and during 10 different flights. 

The normal (reference) range for SpO₂ is 95-100 %. At ground level, mean SpO₂ of the passengers was 97 % (range 93-100). At cruising altitude, which ranged from 37,000 to 41,000 feet, SpO₂ of the passengers was significantly lower: mean 93 % (range 85-98). One passenger had a SpO₂ of 94 % at ground level, which reduced to 85 % at altitude. 

Fifty-four percent (54 %) of the passengers had a SpO₂ less than 94 % during flight. The authors claim this to be the first study to quantify the reduction in oxygen saturation during commercial air travel and suggest that hypoxia may be a contributory factor in air-travel-related morbidity.